The chine is the portion of the hull of a flat or V-bottomed boat that forms the intersection between the side and bottom of the hull. The chine may be “hard” (a well defined edge) or “soft” (significant rounding, often merely a gentle curve with no definitive break between bottom and side).
Many power boats have a chine with a step or recess to allow air to be introduced under the hull, often referred to as “vented” chine. Air is introduced under the hull through the vented chine. The introduction of air reduces the wetted area of the hull to lower hydrodynamic drag.
A disadvantage of conventional vented chines is that they can reduce stability during turns, particularly at high speeds. The introduction of air under the hull and resulting decrease in wetted surface area reduces stability. Furthermore, the removal of a portion of the chine to form the vent can further reduce stability during turns by eliminating part of the turning rail. Consequently, high speed turns frequently induce sideways skidding in boats with vented chines. Manufacturers of power boats with vented chines often caution against hard turns at speeds over 40 miles per hour.
Another handling problem commonly encountered when operating power boats is the tendency of the stern to wag from side-to-side at slow speeds. This phenomenon is often called “stern wander”. At idle speeds, conventional transoms cause turbulence at the stern as water rushes from the sides into the channel left behind the boat as it travels through the water. This turbulence pulls the stern of the boat resulting in a haphazard oscillation. When traveling at slow speeds, the driver must turn the wheel back and forth to overcome this stern oscillation. Stem wander can create a safety risk because the stern is oscillating out of control (for example, by bringing the prop in contact with people or objects in the water around the stern), or because the driver is distracted as a result of efforts to control the oscillation.
Thus, there is a significant need for an improved vessel hull design that includes features for increasing stability during turns and/or for decreasing stern wander. The modifications to hull design described herein can increase stability during turns and can decrease stern wander as compared to similar hulls without the disclosed modifications.